1. Field Of The Invention
The present invention relates to improvements in medical instruments. More particularly, the present invention relates to an improved apparatus to catheterize a human urethra so as to avoid bacterial contamination resultant from such procedure and a method for its use.
2. Description Of The Prior Art
One of the most common medical procedures is the insertion of a medical instrument into a body passage, for example, the insertion of a catheter through the urethra into the bladder.
Despite significant advances in medical technology, however, this procedure continues to give rise to high incidence of infection in the upper urinary tract and bladder. This is because the urethra, and especially the male urethra, is unsterile for a certain portion of its length. In this connection, the National Center for Disease Control has determined that the first three inches of the male urethra is contaminated with various infectious agents, whereas the infectious area of the female urethra is only about one and one half inches.
It is standard practice for catheterization to be performed only after the area around the urethra has been thoroughly cleaned, the catheter has been sterilized and the operator has donned surgical gloves and mask. Despite this precaution, subsequent urinary tract infection is still commonplace. The reason for this has been identified as resulting from bacteria which are present within the urethra itself, particularly at its outer end. Such bacteria is difficult, if not impossible, to remove prior to insertion of the catheter.
The urethra is naturally provided with a defense mechanism to prevent the migration of bacteria into the upper urinary tract and ultimately the bladder. This defense mechanism has been described as a high pressure area located in the intermediate urinary tract, the presence of which defines a sterile area immediately below the bladder. As the catheter is introduced into urethra, however, it comes into contact with the bacteria residing in the contaminated lower zone and carries these agents along the urethra and into the bladder, thereby resulting in infection.
No amount of pre-cleaning of the area external of the urethra will generally prevent infection of the type described above which results from catheterization.
Several proposals have been made to prevent the catheter from carrying bacteria along the urinary tract, but none of these have proved entirely successful, resulting in the general failure of the apparatus and techniques associated with such proposals to achieve commercial success. For example, U.S. Pat. Nos. 3,332,424 (Minteer), 3,908,635 (Vick) and 3,908,663 (Vick) describe assemblies having a catheter tube of thin flexible material and a rigid collar secured around one end of the catheter tube. In use, these catheters are operated by placing the collar around the entrance to the body passage and pushing the tube through the collar so that the tube progressively everts along the passage. In this way movement of the tube wall relative to the passage wall is reduced so that bacteria are less likely to be carried along the passage.
Notwithstanding these designs, bacteria can nevertheless be forced into the leading open end of the catheter tube as it everts, and then be discharged and redeposited further up the passage on continued eversion of the tube. Therefore, while these previously proposed catheters represent an improvement over a basic catheter tube, they nevertheless cause a degree of contamination by carrying bacteria further up the urethral passage.
U.S. Pat No. 3,669,099 (Silverman) describes a similar system to the above-described prior art in that it discloses an everting tubing for contacting a body cavity wall. In the Silverman patent, however, the ends of the tubing are secured and sealed to a rigid cylindrical tube surrounding the tubing so that the tubing forms a closed toroidal chamber which is then filled with a fluid. A long cylindrical medical instrument can then be pushed through the tubing and the pressure of fluid causes the tubing to evert as the instrument passes through it.
The previously proposed arrangement is complex as a fluid inlet must be provided in the rigid tube for injection of fluid to an appropriate pressure, and the presence of the toroidal chamber makes the apparatus rather wide and therefore somewhat uncomfortable for the patient. It is also relatively expensive to manufacture.
Responsive to the above problems, urinary catheter designs have been proposed which incorporate an axial sheath through which is inserted a smaller diameter catheter. U.S. Pat. No. 3,421,509 (Fiore) and West German Offenlegungsschrift No. 24 56 980 both have a urethral catheter in which the catheter tube is slidable within an impervious-walled sheath having a closure member in the form of overlapping flaps at its distal end. The sheath also has an external shoulder for engaging the mouth of the urethra to limit the extent of insertion of the sheath into the urethra. In Fiore the shoulder is stated to be about 1.5 inches from the distal end of the sheath. U.S. Pat. No. 4,023,559 (Gaskell) also has a catheter tube slidable within an impervious-walled sheath which has a closure formation at its distal end through which the catheter tube can extend. In the Gaskell design, no limitation is provided on the sheath to determine its extent of penetration. A sheathed design is also described in U.S. Patent No. 4,652,259 as issued to O'Neil. The sheath proposed by O'Neil is inserted through the contaminated lower tract upward in the urinary tract to a previously non-contaminated zone. In this fashion, the O'Neil assembly was proposed to act like a bridge over the contaminated area.
Disadvantages with these designs, however, also arise in the movement of bacteria upward in the urinary tract upon insertion of the catheter assembly by contamination of the sheath during placement in the urethra. Notwithstanding the bridging effect of the sheath, it becomes contaminated during its passage through the infected area of the urethra and thus spreads these infectious agents to the catheter. Hence, these designs also provide for the opportunity of bacterial infection during the catheterization procedure.